The present invention relates to hydraulic breaking hammers of the kind that comprise a machine housing which includes a cylinder bore and a reciprocatingly movable impact piston which moves backwards and forwards in said cylinder bore in response to alternating hydraulic pressure, a tool part which is fitted to the front of the machine housing and which has a guide bore which lies in line with the cylinder bore and in which a breaking tool is slidably carried and repeatedly subjected to impact by the impact piston as it moves, support means for aligning the breaking hammer mechanically in operation, and sealing means arranged in the front of the machine housing between the cylinder bore and the impact piston and functioning to separate the drive hydraulics of the breaking hammer from the tool part.
Breaking hammers of this kind are normally mounted on hydraulically operated carriers of different sizes, wherein the carrier hydraulics are also coupled to drive the breaking hammer, and wherein the breaking hammer is pivotally mounted on the outer end of a boom via the supports on said housing so as to be positioned mechanically by said boom in operation.
The machine housing of the breaking hammer is typically comprised of separate cylinder parts which embrace the impact piston, the seals and the valve system, and which are grouped axially in juxtaposed relationship and held tightly together by robust side bolts, so as to ensure that a seal is obtained between the cylinder parts against the high internal hydraulic working pressures. Side bolts and other screw fastener means, however, have certain drawbacks. The screw threads are shaken loose. In the case of side bolts, the wear and the corrosion that occurs in operation, together with micro-movements in the joints as a result of impacts and vibrations generated in the breaking hammer, cause the joints of the cylinder parts and their seals to be attacked by penetrating pressure oil and leakages and ultimately result in conditions which are hazardous both to the surroundings and to people in the vicinity of the work being carried out. Side bolts can also fracture, with serious consequences. In recent times, this insight into the hazards of side bolts has led to an endeavour to exclude side bolts from breaking hammer constructions. An example of one such endeavour is disclosed in International Publication WO 93/22106, PCT/SE93/00382.
Lightweight automotive carriers and short breaking hammers have been used in the demolition of derelict buildings, so as to be able to enter confined spaces more easily and to work therein more effectively. The hydraulic part of the machine housing forms the rear part of the breaking hammer and can therewith readily be made short and sufficiently robust to provide a long useful life, in the absence of side bolts. However, indoor demolition work results in an increase in laterally acting impacts, blows and breaking action, particularly against the breaking tool and against the tool part at the front of the housing, such that after being in operation for some length of time, the entire machine housing may be judged to be ineffective due to damage to the tool part. This is highly disadvantageous from the cost aspect, in view of the fact that the hydraulic part of the tool is expensive to produce and cannot be considered as being a spare part.